Multi-layer piezoelectric substrate with heat dissipation

ABSTRACT

Aspects of this disclosure relate to a filter that includes an acoustic wave device with a multi-layer substrate with heat dissipation. The multi-layer substrate includes a support substrate (e.g., a quartz substrate), a piezoelectric layer, an interdigital transducer electrode on the piezoelectric layer, and a thermally conductive layer configured to dissipate heat associated with the acoustic wave device. The thermally conductive layer is disposed between the support substrate and the piezoelectric layer. The thermally conductive layer has a thickness that is greater than 10 nanometers and less than a thickness of the piezoelectric layer.

CROSS REFERENCE TO PRIORITY APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/674,342, filed May 21, 2018 and titled“TEMPERATURE COMPENSATED MULTI-LAYER PIEZOELECTRIC SUBSTRATE,” and U.S.Provisional Patent Application No. 62/681,456, filed Jun. 6, 2018 andtitled “TEMPERATURE COMPENSATED MULTI-LAYER PIEZOELECTRIC SUBSTRATE,”the disclosures of each of which are hereby incorporated by reference intheir entireties herein.

BACKGROUND Technical Field

Embodiments of this disclosure relate to surface acoustic wave devices.

Description of Related Technology

Acoustic wave filters can be implemented in radio frequency electronicsystems. For instance, filters in a radio frequency front end of amobile phone can include acoustic wave filters. An acoustic wave filtercan be a band pass filter. A plurality of acoustic wave filters can bearranged as a multiplexer. For example, two acoustic wave filters can bearranged as a duplexer.

A surface acoustic wave filter can include a plurality of resonatorsarranged to filter a radio frequency signal. Each resonator can includea surface acoustic wave device. A surface acoustic wave resonator caninclude an interdigital transductor electrode on a piezoelectricsubstrate. The surface acoustic wave resonator can generate a surfaceacoustic wave on a surface of the piezoelectric layer on which theinterdigital transductor electrode is disposed. Filtering signals havingrelatively high power levels with surface acoustic wave resonators cangenerate heat.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

The innovations described in the claims each have several aspects, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of the claims, some prominent features ofthis disclosure will now be briefly described.

One aspect of this disclosure is a filter with a multi-layer substratewith heat dissipation. The filter includes an acoustic wave device. Thefilter is arranged as a band pass filter configured to filter a radiofrequency signal. The acoustic wave device includes a support substrate,a piezoelectric layer, an interdigital transducer electrode on thepiezoelectric layer, and a thermally conductive layer configured todissipate heat associated with the acoustic wave device. The thermallyconductive layer has a higher thermal conductivity than the supportsubstrate. The thermally conductive layer is disposed between thesupport substrate and the piezoelectric layer. The thermally conductivelayer has a thickness that is greater than 10 nanometers and less than athickness of the piezoelectric layer.

The support substrate can be a quartz substrate. The support substratecan include at least one of silicon, aluminum nitride, silicon nitride,magnesium oxide spinel, magnesium oxide crystal, or diamond. Thepiezoelectric layer can have a higher thermal conductivity than thesupport substrate.

The acoustic wave device is configured to generate an acoustic wavehaving a wavelength of λ, and the thickness of the thermally conductivelayer can be less than 0.03 λ. The thickness of the thermally conductivelayer can be less than half of the thickness of the piezoelectric layer.

The acoustic wave device can further include a temperature compensatinglayer having a positive temperature coefficient of frequency, in whichthe temperature compensating layer is disposed between the piezoelectriclayer and the support substrate. The temperature compensating layer canbe a silicon dioxide layer. The temperature compensating layer can bedisposed between the piezoelectric layer and the thermally conductivelayer. The temperature compensating layer can be disposed between thethermally conductive layer and the support substrate. The temperaturecompensating layer can be disposed on an opposite side of thepiezoelectric layer than the interdigital transducer electrode.

The acoustic wave device can include a first temperature compensatinglayer disposed between the piezoelectric layer and the thermallyconductive layer, and a second temperature compensating layer disposedbetween the thermally conductive layer and the quartz substrate.

The thermally conductive layer can include a metal. The thermallyconductive layer can include aluminum in certain applications. Thethermally conductive layer can have a thermal conductivity that is atleast 10 times a thermal conductivity of the piezoelectric layer. Thepiezoelectric layer can be a lithium tantalate layer. The thermallyconductive layer can have a thermal conductivity in a range from 140W/mK to 425 W/mK.

The filter can be arranged such that a maximum surface temperature of afilter chip that includes the filter is less than 60° Celsius duringoperation of the filter.

Another aspect of this disclosure is a surface acoustic wave device witha temperature compensated multi-layer substrate. The surface acousticwave device includes a support substrate, a piezoelectric layer, aninterdigital transducer electrode on the piezoelectric layer, athermally conductive layer configured to dissipate heat associated withthe surface acoustic wave device, and a temperature compensating layerhaving a positive temperature coefficient of frequency. The thermallyconductive layer has a higher thermal conductive than the supportsubstrate. The thermally conductive layer is disposed between the quartzsubstrate and the piezoelectric layer. The thermally conductive layerhas a thickness that is greater than 10 nanometers and less than athickness of the piezoelectric layer. The temperature compensating layerand the interdigital transducer electrode are disposed on opposite sidesof the piezoelectric layer.

In certain embodiments, the piezoelectric layer is a lithium tantalatelayer and the support substrate is a quartz layer. The surface acousticwave device is configured to generate a surface acoustic wave having awavelength of λ. In certain embodiments, the thickness of the thermallyconductive layer is less than 0.03 λ.

The temperature compensating layer can be a silicon dioxide layer. Thetemperature compensating layer can be disposed between the piezoelectriclayer and the support substrate. The temperature compensating layer canbe disposed between the thermally conductive layer and the piezoelectriclayer. The surface acoustic wave device can include temperaturecompensating layers on opposing sides of the thermally conductive layer.

The thermally conductive layer can include a metal. The thermallyconductive layer can have a thermal conductivity that is at least 10times a thermal conductivity of the piezoelectric layer. The thermallyconductive layer can have a thermal conductivity in a range from 60 W/mKto 425 W/mK. The thermally conductive layer can have a thermalconductivity in a range from 140 W/mK to 300 W/mK.

Another aspect of this disclosure is a filter with a temperaturecompensated multi-layer substrate. The filter is arranged as a band passfilter configured to filter a radio frequency signal. The filterincludes an acoustic wave device. The acoustic wave device includes aquartz substrate, a piezoelectric layer, an interdigital transducerelectrode on the piezoelectric layer, and a thermally conductive layerconfigured to dissipate heat associated with the acoustic wave device.The thermally conductive layer is disposed between the quartz substrateand the piezoelectric layer. The thermally conductive layer has athickness that is greater than 10 nanometers and less than a thicknessof the piezoelectric layer.

The acoustic wave device can further include a temperature compensatinglayer having a positive temperature coefficient of frequency, in whichthe temperature compensating layer is disposed between the piezoelectriclayer and the quartz substrate. The temperature compensating layer canbe a silicon dioxide layer. The temperature compensating layer can bedisposed between the piezoelectric layer and the thermally conductivelayer. The temperature compensating layer can be disposed between thethermally conductive layer and the quartz substrate. The temperaturecompensating layer can be disposed on an opposite side of thepiezoelectric layer than the interdigital transducer electrode.

The acoustic wave device can include a first temperature compensatinglayer disposed between the piezoelectric layer and the thermallyconductive layer, and a second temperature compensating layer disposedbetween the thermally conductive layer and the quartz substrate.

The acoustic wave device is configured to generate an acoustic wavehaving a wavelength of λ, and the thickness of the thermally conductivelayer can be less than 0.03 λ. The thickness of the thermally conductivelayer can be less than half of the thickness of the piezoelectric layer.

The thermally conductive layer can include a metal. The thermallyconductive layer can have a thermal conductivity that is at least 10times a thermal conductivity of the piezoelectric layer. The thermallyconductive layer can have a thermal conductivity in a range from 60 W/mKto 425 W/mK. The thermally conductive layer can have a thermalconductivity in a range from 140 W/mK to 300 W/mK.

The thermally conductive layer can be in physical contact with thepiezoelectric layer. The piezoelectric layer can be a lithium tantalatelayer. The piezoelectric layer can be a lithium niobate layer.

The filter can be arranged such that a maximum surface temperature of afilter chip that includes the filter is less than 60° Celsius duringoperation of the filter.

Another aspect of this disclosure is a surface acoustic wave device witha temperature compensated multi-layer substrate. The surface acousticwave device includes a quartz substrate, a piezoelectric layer, aninterdigital transducer electrode on the piezoelectric layer, athermally conductive layer configured to dissipate heat associated withthe surface acoustic wave device, and a temperature compensating layerhaving a positive temperature coefficient of frequency. The thermallyconductive layer is disposed between the quartz substrate and thepiezoelectric layer. The thermally conductive layer has a thickness thatis greater than 10 nanometers and less than a thickness of thepiezoelectric layer. The temperature compensating layer and theinterdigital transducer electrode are disposed on opposite sides of thepiezoelectric layer.

The temperature compensating layer can be a silicon dioxide layer. Thetemperature compensating layer can be disposed between the piezoelectriclayer and the quartz substrate. The temperature compensating layer canbe disposed between the thermally conductive layer and the piezoelectriclayer.

The surface acoustic wave device can include a second temperaturecompensating layer disposed between the thermally conductive layer andthe quartz substrate.

The surface acoustic wave device is configured to generate a surfaceacoustic wave having a wavelength of λ, and the thickness of thethermally conductive layer can be less than 0.03 λ.

The thermally conductive layer can include a metal. The thermallyconductive layer can have a thermal conductivity that is at least 10times a thermal conductivity of the piezoelectric layer. The thermallyconductive layer can have a thermal conductivity in a range from 60 W/mKto 425 W/mK. The thermally conductive layer can have a thermalconductivity in a range from 140 W/mK to 300 W/mK.

The piezoelectric layer can be a lithium tantalate layer. Thepiezoelectric layer can include lithium. The piezoelectric layer can bea synthetic crystal layer.

Another aspect of this disclosure is a radio frequency module thatincludes a radio frequency switch configured to pass a radio frequencysignal, a surface acoustic wave filter configured to filter the radiofrequency signal, and a package enclosing the surface acoustic wavefilter and the radio frequency switch. The surface acoustic wave filterincludes a support substrate (for example, a quartz substrate), apiezoelectric layer, and a thermally conductive layer configured todissipate heat associated with the acoustic wave device. The thermallyconductive layer is disposed between the support substrate and thepiezoelectric layer.

The radio frequency module can further include a power amplifierconfigured to generate the radio frequency signal, in which the poweramplifier is enclosed within the package. The radio frequency module caninclude any suitable features of the filters and/or surface acousticwave devices discussed herein.

Another aspect of this disclosure is a wireless communication devicethat includes a surface acoustic wave filter configured to provide afiltered radio frequency signal and an antenna configured to transmitthe filtered radio frequency signal. The surface acoustic wave filterincludes a support substrate (for example, a quartz substrate), apiezoelectric layer, and a thermally conductive layer configured todissipate heat associated with the acoustic wave device. The thermallyconductive layer is disposed between the support substrate and thepiezoelectric layer.

The wireless communication device can be a mobile phone. The wirelesscommunication device can further include an antenna switch coupledbetween the surface acoustic wave filter and the antenna. The wirelesscommunication device can include a transceiver in communication with aradio frequency front end, in which the radio frequency front endincludes the surface acoustic wave device. The wireless communicationdevice can include a baseband processor in communication with thetransceiver.

The wireless communication device can include any suitable features ofthe filters and/or surface acoustic wave devices and/or radio frequencymodules discussed herein.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the innovations have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment. Thus, theinnovations may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will now be described, by way ofnon-limiting example, with reference to the accompanying drawings.

FIG. 1 illustrates a cross section of a surface acoustic wave devicewith a multi-layer piezoelectric substrate with heat dissipationaccording to an embodiment.

FIG. 2A illustrates a cross section of a baseline surface acoustic wavedevice.

FIG. 2B illustrates a cross section of a surface acoustic wave devicewith a multi-layer piezoelectric substrate with heat dissipationaccording to an embodiment.

FIG. 3A illustrates a chip surface temperature distribution of thebaseline surface acoustic wave device of FIG. 2A.

FIG. 3B illustrates a chip surface temperature distribution of thesurface acoustic wave device of FIG. 2B.

FIG. 4A is a graph with curves for chip temperature as a function ofthickness of a thermally conductive layer of the surface acoustic wavedevice of FIG. 2B.

FIG. 4B is a graph with curves for simulated filter performance forvarious thicknesses of a thermally conductive layer of the surfaceacoustic wave device of FIG. 2B.

FIG. 5 is a graph that shows thermal conductivities of variousmaterials.

FIG. 6 is a graph with curves for chip temperature as a function ofthickness for various thermally conductive layers included in place ofthe thermally conductive layer of a surface acoustic wave device of FIG.2B.

FIG. 7 illustrates a cross section of a surface acoustic wave devicewith a temperature compensated multi-layer piezoelectric substrateaccording to an embodiment.

FIG. 8 illustrates a cross section of a surface acoustic wave devicewith a temperature compensated multi-layer piezoelectric substrateaccording to another embodiment.

FIG. 9 illustrates a cross section of a surface acoustic wave devicewith a temperature compensated multi-layer piezoelectric substrateaccording to another embodiment.

FIG. 10 is a schematic block diagram of a module that includes a poweramplifier, a switch, and filters in accordance with one or moreembodiments.

FIG. 11 is a schematic block diagram of a module that includes poweramplifiers, switches, and filters in accordance with one or moreembodiments.

FIG. 12 is a schematic block diagram of a module that includes poweramplifiers, switches, filters in accordance with one or moreembodiments, and an antenna switch.

FIG. 13 is a schematic block diagram of a wireless communication devicethat includes filters in accordance with one or more embodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

A higher quality factor (Q) and a temperature coefficient of frequency(TCF) closer to zero can be desirable in acoustic wave devices. Asurface acoustic wave resonator that includes quartz crystal bonded witha lithium tantalate (LiTaO₃) piezoelectric layer can achieve arelatively high Q and a TCF that is relatively close to zero. A surfaceacoustic wave device with a lithium tantalate substrate bonded with aquartz crystal can experience undesirable self-heating due to thethermal conductivity of the quartz crystal being lower than the thermalconductivity of lithium tantalate. The thermal conductivity of a lithiumniobate (LiNbO₃) or a lithium tantalate piezoelectric layer of a surfaceacoustic wave device can present challenges related to self-heating in asurface acoustic wave device. This disclosure provides technicalsolutions to such self-heating.

Aspects of this disclosure relate to an acoustic wave resonator thatincludes a thermally conductive layer between a support substrate (e.g.,a quartz crystal substrate) and a piezoelectric substrate (e.g., alithium tantalate substrate). The thermally conductive layer can improveone or more of substrate adhesion, heat dissipation, and electriccharacteristics relative to a similar device without the thermallyconductive layer. The thermally conductive layer can be a layer ofmaterial having a thermal conductivity that is higher than the thermalconductivity of the support substrate. Thermal conductivity comparisonsherein can be for different materials at the same temperature. Thethermally conductive layer can be sufficiently thick to dissipate heatfrom self-heating. The thermally conductive layer can also be relativelythin. The acoustic wave resonator is an acoustic wave device. Theacoustic wave resonator can be included in a band pass filter configuredto filter a radio frequency (RF) signal.

FIG. 1 illustrates a cross section of a surface acoustic wave device 10with a multi-layer piezoelectric substrate with heat dissipationaccording to an embodiment. The illustrated surface acoustic wave device10 includes a support substrate 12, a thermally conductive layer 14, apiezoelectric layer 16, an interdigital transducer (IDT) electrode 18,and reflective gratings 19. The thermally conductive layer 14 candissipate heat associated with the surface acoustic wave device 10.Self-heating of the acoustic wave device 10 is reduced by including thethermally conductive layer 14. Accordingly, the surface acoustic wavedevice 10 includes a multi-layer piezoelectric substrate with heatdissipation. The thermally conductive layer 14 can improve adherencebetween the layers of the surface acoustic wave device 10. Electricalperformance of the surface acoustic wave device 10 can improve with thethermally conductive layer 14.

The support substrate 12 can be a quartz substrate. A quartz supportsubstrate can contribute to the surface acoustic wave device 10achieving a relatively high Q. The support substrate 12 can be a silicon(Si) substrate, an aluminum nitride (AlN) substrate, a silicon nitride(SiN) substrate, a magnesium oxide (MgO) spinel substrate, a magnesiumoxide crystal substrate, a diamond substrate, or the like. The supportsubstrate 12 can have a relatively high impedance. The support substrate12 can have a lower thermal conductivity than the thermally conductivelayer 14. The thermal conductivity of the support substrate 12 can belower than the thermal conductivity of the piezoelectric layer 16. Forexample, the support substrate 12 can be quartz and the piezoelectriclayer 16 can be lithium tantalate and quartz has a lower thermalconductivity than lithium tantalate. The support substrate 12 can bebonded with the thermally conductive layer 14. The support substrate 12can be in physical contact with the thermally conductive layer 14 asillustrated.

The surface acoustic wave device 10 includes a thermally conductivelayer 14 disposed between the support substrate 12 and the piezoelectriclayer 16. In the surface acoustic wave device 10, the thermallyconductive layer 14 and the IDT electrode 18 are on opposite sides ofthe piezoelectric layer 16.

The thermally conductive layer 14 has a higher thermal conductivity thanthe piezoelectric layer 16. In certain applications, the thermalconductivity of the thermally conductive layer 14 is at least 10 times athermal conductivity of the piezoelectric layer 16.

The thermally conductive layer 14 can have a thermal conductivity in arange from 60 W/mK to 425 W/mK. In certain applications, the thermallyconductive layer 14 can have a thermal conductivity in a range from 140W/mK to 300 W/mK. In some applications, the thermally conductive layer14 can have a thermal conductivity in a range from 140 W/mK to 425 W/mK.The thermally conductive layer 14 can include a metal. For example, thethermally conductive layer 14 can include aluminum (Al), silver (Ag),gold (Au), copper (Cu), tungsten (W), titanium (Ti), nickel (Ni), iron(Fe), the like, or any suitable combination thereof. As one example, thethermally conductive layer 14 can be an aluminum layer. In certainapplications, the thermally conductive layer 14 can be a layer of any ofthe following materials: silicon nitride (SiN), aluminum nitride (AlN),titanium nitride (TiN), silicon-oxynitride (SiON), tantalum silicondioxide (TaSiO₂), a metal compound including titanium (Ti), or a metalcompound including stainless steel (e.g., by using an ion gun surfaceactivation bonding process). The material of the thermally conductivelayer 14 can be selected based on its thermal dispersion and/orelectrical performance of a surface acoustic wave device that includessuch a thermally conductive layer of the material.

The piezoelectric layer 16 can be any suitable piezoelectric layer. Thepiezoelectric layer 16 is a lithium tantalate layer in certainapplications. The piezoelectric layer 16 can be a lithium niobate layerin some instances. Accordingly, the piezoelectric layer 16 can be alithium based piezoelectric layer. The piezoelectric layer 16 can be asynthetic crystal layer.

The IDT electrode 18 is disposed on piezoelectric layer 16. The IDTelectrode 18 can have a pitch that sets the wavelength λ of a surfaceacoustic wave generated by the surface acoustic wave device 10. The IDTelectrode 18 can be an aluminum IDT electrode. IDT electrode materialcan include aluminum (Al), titanium (Ti), gold (Au), silver (Ag), copper(Cu), platinum (Pt), tungsten (W), molybdenum (Mo), ruthenium (Ru), orany suitable combination thereof. In some instances, the IDT electrode18 can be a multi-layer IDT electrode. For instance, the IDT electrode16 can include aluminum and molybdenum in certain applications.

The surface acoustic wave device 10 includes reflective gratings 19 onthe piezoelectric layer 16. As illustrated, the reflective gratings 19are arranged to reflect acoustic energy. Accordingly, the gratings canbe referred to as acoustic reflectors. The reflective gratings 19 caninclude a plurality of periodically distributed relatively thin metalstrips. The metal strips of one or more of the gratings 19 can beelectrically connected in parallel with each other. Because these metalstrips are part of the acoustically active area of a surface acousticwave filter, the electrode geometry can be precisely controlled.

FIG. 2A illustrates a cross section of a baseline surface acoustic wavedevice 20. The baseline surface acoustic wave device 20 includes aquartz substrate 22 having a thickness of H₂, a lithium tantalate layer26 having a thickness of H₁, an interdigital IDT electrode 18 on thelithium tantalate layer 26, and reflective gratings 19 on the lithiumtantalate layer 26. The quartz substrate 22 and the lithium tantalatelayer 26 are bonded with each other and in physical contact with eachother in the surface acoustic wave device 20.

FIG. 2B illustrates a cross section of a surface acoustic wave device 25with a multi-layer piezoelectric substrate with heat dissipationaccording to an embodiment. The surface acoustic wave device 25 includesa quartz substrate 22 having a thickness of H₂, a lithium tantalatelayer 26 having a thickness of H₁, an aluminum layer 24 having athickness of H₃, an interdigital IDT electrode 18 on the lithiumtantalate layer 26, and reflective gratings 19 on the lithium tantalatelayer 26. The quartz substrate 22 is an example of the support substrate12 of FIG. 1. The aluminum layer 24 is an example of the thermallyconductive layer 14 of FIG. 1. The lithium tantalate layer 26 is anexample of the piezoelectric layer 16 of FIG. 1. In the surface acousticwave device 25, the aluminum layer 24 is disposed between the quartzsubstrate 22 and the lithium tantalate layer 26. The illustratedaluminum layer 24 has a first side in physical contact with the quartzsubstrate 22 and a second side in physical contact with the lithiumtantalate layer 26.

FIG. 3A illustrates a chip surface temperature distribution of thebaseline surface acoustic wave device 20 of FIG. 2A. FIG. 3A indicatesthat a surface acoustic wave chip with a baseline surface acoustic wavedevice 20 with a quartz substrate 22 with a thickness H₂ of 100 um and alithium tantalate layer 26 with a thickness H₁ of 100 um can have amaximum surface temperature of 83.5° C.

FIG. 3B illustrates a chip surface temperature distribution of thesurface acoustic wave device 25 of FIG. 2B. FIG. 3B indicates that asurface acoustic wave chip with a surface acoustic wave device 25 with aquartz substrate 22 with a thickness H₂ of 100 um, a lithium tantalatelayer 26 with a thickness H₁ of 100 um, and a thermally conductive layerwith a thickness H₃ of 30 nm can have a maximum surface temperature of52.2° C. Accordingly, FIGS. 3A and 3B indicate that including thealuminum layer 24 between the quartz substrate 22 and the lithiumtantalate layer 26 can reduce surface chip temperature significantly.FIG. 3B corresponds to an embodiment of a surface acoustic wave devicethat can achieve a maximum surface temperature of 60° C. or less. Othersuitable thermally conductive layers with a higher thermal conductivitythan lithium tantalate can be implemented in place of the aluminum layer24.

FIG. 4A is a graph with curves for chip temperature as a function ofthickness of the aluminum layer 24 of the surface acoustic wave device25 of FIG. 2B. Three curve are shown corresponding to differentthicknesses of the lithium tantalate layer 26. These curves indicatethat the chip temperature decreases more for thinner lithium tantalatelayers 26. Chip temperature can generally decrease for thinnerpiezoelectric layers. Chip temperature can generally decrease forthicker thermally conductive layers. The impact of the thickness of thethermally conductive layer dissipating heat can be independent of awavelength of a surface acoustic wave generated by the surface acousticwave device 25. FIG. 4A indicates that the aluminum layer 24 of thesurface acoustic wave device 25 can significantly improve thermaldissipation for thicknesses H₃ of at least 10 nm. With a relatively thinpiezoelectric layer and a thermally conductive layer, the surfaceacoustic wave device 25 of FIG. 2B can have an improved powerdurability.

Electrical performance of a surface acoustic wave device can degradewhen the thickness H₃ of the thermally conductive layer is too thick.Accordingly, an upper bound for the thickness H₃ of the thermallyconductive layer can be set by the electrical performance of a surfaceacoustic wave device that includes the thermally conductive layer. Theupper bound can be determined based on a waveform of such a surfaceacoustic wave device. The upper bound for the thickness H₃ of thethermally conductive layer can depend on the material of the thermallyconductive layer.

FIG. 4B is a graph with curves for simulated filter performance forvarious thicknesses of a thermally conductive layer of the surfaceacoustic wave device of FIG. 2B. The illustrated curves correspond tothermally conductive layer thicknesses H₃ of 0 λ (no thermallyconductive layer like the surface acoustic wave device 20 of FIG. 2A),0.01 λ, 0.02 λ, and 0.03 λ, in which λ is the wavelength of a surfaceacoustic wave generated by the surface acoustic wave device 25. Theupper bound on the thicknesses H₃ of the thermally conductive layer 14can be proportional to wavelength. As shown in FIG. 4B, the electricalperformance starts to degrade for thermally conductive layer thicknessesH₃=0.02 λ. FIG. 4B indicates that the electrical performance is degradedfor thermally conductive layer thicknesses H₃=0.03 λ. Accordingly, thethermally conductive layer thicknesses H₃ of the surface acoustic wavedevice 25 can be less than 0.03 λ so that electrical performance of thesurface acoustic wave device 25 is not significantly degraded. As anexample, for λ=4.0 um, H₃ can be less than 120 nm. As another example,for λ=2.0 um, H₃ can be less than 60 nm.

FIG. 5 is a graph that shows thermal conductivities of various materialsincluding Si, AN, SiN, Al, Ag, Au, Cu, W, Ti, Ni, and Fe. Thesematerials have higher thermal conductivities than lithium tantalate andlithium niobate.

FIG. 6 is a graph with curves for chip temperature as a function ofthickness for various thermally conductive layers included in place ofthe aluminum layer 24 of the surface acoustic wave device 25 of FIG. 2B.A curve corresponding to each of the thermally conductive layer of eachof the materials included in the graph of FIG. 5 is included in FIG. 6.

The thickness H₃ of the thermally conductive layer can be at least 10nm. As shown in FIGS. 4A and 6, a thermally conductive layer with athickness H₃ of at 10 nm can significantly reduce maximum chiptemperature. The thickness H₃ of the thermally conductive layer can beless than 0.03 λ as indicated by FIG. 4B so that the thermallyconductive layer does not significantly degrade electrical performance.Accordingly, the thermally conductive layer 14 of the surface acousticwave device 25 can have a thickness H₃ in a range from 10 nm to 0.03 λ,in which λ is the wavelength of a surface acoustic wave generated by thesurface acoustic wave device 25.

A temperature compensating layer can be added between the piezoelectriclayer and the quartz substrate of the surface acoustic wave device ofFIG. 1 and/or FIG. 2B. Such a temperature compensation layer can bringthe temperature coefficient of frequency (TCF) of such a surfaceacoustic wave device closer to zero than the surface acoustic wavedevice of FIG. 1 or the surface acoustic wave device of FIG. 2B.Accordingly, there can be less variation with temperature for thesurface acoustic wave device with the temperature compensating layer.This can be significant in certain applications. The temperaturecompensation layer can have a positive TCF to compensate for a negativeTCF of certain piezoelectric layers, such as lithium niobate or lithiumtantalate piezoelectric layers. FIGS. 7 to 9 illustrate surface acousticwave devices that include a temperature compensating layer in amulti-layer piezoelectric substrate with heat dissipation. In certainapplications, surface acoustic wave devices of FIGS. 7 to 9 can includelithium tantalate piezoelectric layers and quartz support substrates.Any suitable principles and advantages of these surface acoustic wavedevices can be combined with each other and/or with any of the othersurface acoustic wave devices discussed herein.

FIG. 7 illustrates a cross section of a surface acoustic wave device 70with a temperature compensated multi-layer piezoelectric substrateaccording to an embodiment. The surface acoustic wave device 70 is likethe surface acoustic wave device 10 of FIG. 1, except that a temperaturecompensating layer 72 is included between the support substrate 12 andthe piezoelectric layer 16 in the surface acoustic wave device 70. Thetemperature compensating layer 72 can be silicon dioxide (SiO₂) layer.The temperature compensating layer 72 can be a layer of any othersuitable material that brings TCF closer to zero, such as a materialhaving a positive temperature coefficient of frequency. For instance,the temperature compensating layer 72 can be a tellurium dioxide (TeO₂)layer or a silicon oxyfluoride (SiOF) layer. The temperaturecompensating layer 72 can include any suitable combination of SiO₂,TeO₂, and/or SiOF. As illustrated in FIG. 7, the temperaturecompensating layer 72 is disposed between the thermally conductive layer14 and the piezoelectric layer 16. The temperature compensating layer 72can have a first side in physical contact with the thermally conductivelayer 14 and a second side in physical contact with the piezoelectriclayer 16, in which the first side and the second side are opposing sidesof the temperature compensating layer 72.

FIG. 8 illustrates a cross section of a surface acoustic wave device 80with a temperature compensated multi-layer piezoelectric substrateaccording to another embodiment. The surface acoustic wave device 80 islike the surface acoustic wave device 70 of FIG. 7, except that atemperature compensating layer 72 is disposed between the supportsubstrate 12 and the thermally conductive layer 14 in the surfaceacoustic wave device 80. As illustrated in FIG. 8, the thermallyconductive layer 14 and the support substrate 12 can be in physicalcontact with opposing sides of the temperature compensating layer 72.

FIG. 9 illustrates a cross section of a surface acoustic wave device 90with a temperature compensated multi-layer piezoelectric substrateaccording to another embodiment. The surface acoustic wave device 90 islike the surface acoustic wave device 70 of FIG. 7, except that thethermally conductive layer 14 is disposed between two temperaturecompensating layers 72 and 94. The temperature compensating layers 72and 94 can be silicon dioxide layers. As illustrated in FIG. 9, thetemperature compensating layers 72 and 94 can be in physical contactwith opposing sides of the thermally conductive layer 14.

The acoustic wave devices discussed herein can be implemented in avariety of packaged modules. Some example packaged modules will now bediscussed in which any suitable principles and advantages of theacoustic wave devices discussed herein can be implemented. FIGS. 10, 11,and 12 are schematic block diagrams of illustrative packaged modulesaccording to certain embodiments. Any suitable combination of featuresof these embodiments can be combined with each other.

FIG. 10 is a schematic block diagram of a module 100 that includes apower amplifier 102, a switch 104, and filters 106 in accordance withone or more embodiments. The module 100 can include a package thatencloses the illustrated elements. The power amplifier 102, the switch104, and the filters 106 can be disposed on a common packagingsubstrate. The packaging substrate can be a laminate substrate, forexample. The switch 104 can be a multi-throw radio frequency switch. Theswitch 104 can electrically couple an output of the power amplifier 102to a selected filter of the filters 106. The filters 106 can include anysuitable number of acoustic wave filters. One or more of the acousticwave filters of the filters 106 can be implemented in accordance withany suitable principles and advantages of the acoustic wave devicesdiscussed herein.

FIG. 11 is a schematic block diagram of a module 110 that includes poweramplifiers 102A and 102B, switches 104A and 104B, and filters 106′ inaccordance with one or more embodiments. The module 110 is like themodule 100 of FIG. 10, except that the module 110 includes an additionalpower amplifier 102B and an additional switch 104B and the filters 106′are arranged to filter signals for the signals paths associated with aplurality of power amplifiers 102A and 102B. The different signal pathscan be associated with different frequency bands and/or different modesof operation (e.g., different power modes, different signaling modes,etc.).

FIG. 12 is a schematic block diagram of a module 120 that includes poweramplifiers 102A and 102B, switches 104A and 104B, and filters 106A and106B in accordance with one or more embodiments, and an antenna switch122. The module 120 is like the module 110 of FIG. 11, except the module120 includes an antenna switch 122 arranged to selectively couple asignal from the filters 106A or the filters 106B to an antenna node. Thefilters 106A and 106B can correspond to the filters 106′ of FIG. 11.

FIG. 13 is a schematic block diagram of a wireless communication device130 that includes filters 106 in accordance with one or moreembodiments. The wireless communication device 130 can be any suitablewireless communication device. For instance, a wireless communicationdevice 130 can be a mobile phone, such as a smart phone. As illustrated,the wireless communication device 130 includes an antenna 131, an RFfront end 132, a transceiver 134, a processor 135, and a memory 136. Theantenna 131 can transmit RF signals provided by the RF front end 132.The antenna 131 can provide received RF signals to the RF front end 132for processing.

The RF front end 132 can include one or more power amplifiers, one ormore low noise amplifiers, one or more RF switches, one or more receivefilters, one or more transmit filters, one or more duplexers, or anysuitable combination thereof. The RF front end 132 can transmit andreceive RF signals associated with any suitable communication standards.Any of the surface acoustic wave devices discussed herein can beimplemented in the RF front end 132.

The transceiver 134 can provide RF signals to the RF front end 132 foramplification and/or other processing. The transceiver 134 can alsoprocess an RF signal provided by a low noise amplifier of the RF frontend 132. The transceiver 134 is in communication with the processor 135.The processor 135 can be a baseband processor. The processor 135 canprovide any suitable baseband processing functions for the wirelesscommunication device 130. The memory 136 can be accessed by theprocessor 135. The memory 136 can store any suitable data for thewireless communication device 130.

Although example embodiments may be discussed with filters forillustrative purposes, any suitable the principles and advantagesdisclosed herein can be implement in a multiplexer that includes aplurality of filters coupled together at a common node. Examples ofmultiplexers include but are not limited to a duplexer with two filterscoupled together at a common node, a triplexer with three filterscoupled together at a common node, a quadplexer with four filterscoupled together at a common node, a hexaplexer with six filters coupledtogether at a common node, an octoplexer with eight filters coupledtogether at a common node, or the like. One or more filters of amultiplexer can include a multi-layer piezoelectric substrate surfaceacoustic wave resonator in accordance with any suitable principles andadvantages disclosed herein.

Any of the principles and advantages discussed herein can be applied toother systems, modules, chips, surface acoustic wave devices, filters,duplexers, multiplexers, wireless communication devices, and methods notjust to the systems, modules, filters, multiplexers, wirelesscommunication devices, and methods described above. The elements andoperations of the various embodiments described above can be combined toprovide further embodiments. Any of the principles and advantagesdiscussed herein can be implemented in association with radio frequencycircuits configured to process signals in a frequency range from about30 kilohertz (kHz) to 300 gigahertz (GHz), such as in a range from about450 megahertz (MHz) to 6 GHz. For instance, any of the filters discussedherein can filter signals have a frequency in a range from about 450 MHzto 6 GHz. In some instances, filter that includes an acoustic waveresonator according to an embodiment can filter RF signals atfrequencies up to and including millimeter wave frequencies.

Aspects of this disclosure can be implemented in various electronicdevices. Examples of the electronic devices can include, but are notlimited to, consumer electronic products, parts of the consumerelectronic products such as chips and/or packaged radio frequencymodules, electronic test equipment, uplink wireless communicationdevices, personal area network communication devices, etc. Examples ofthe consumer electronic products can include, but are not limited to, amobile phone such as a smart phone, a wearable computing device such asa smart watch or an ear piece, a telephone, a television, a computermonitor, a computer, a router, a modem, a hand-held computer, a laptopcomputer, a tablet computer, a personal digital assistant (PDA), avehicular electronics system such as an automotive electronics system, amicrowave, a refrigerator, a stereo system, a digital music player, acamera such as a digital camera, a portable memory chip, a householdappliance, etc. Further, the electronic devices can include unfinishedproducts.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” “for example,” “such as” and the like, unlessspecifically stated otherwise or otherwise understood within the contextas used, is generally intended to convey that certain embodimentsinclude, while other embodiments do not include, certain features,elements and/or states. The word “coupled,” as generally used herein,refers to two or more elements that may be either directly coupled toeach other, or coupled by way of one or more intermediate elementsLikewise, the word “connected,” as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosure. Indeed, the novel devices, chips, methods,apparatus, and systems described herein may be embodied in a variety ofother forms. Furthermore, various omissions, substitutions and changesin the form of the methods, apparatus, and systems described herein maybe made without departing from the spirit of the disclosure. Forexample, circuit blocks described herein may be deleted, moved, added,subdivided, combined, and/or modified. Each of these circuit blocks maybe implemented in a variety of different ways. The accompanying claimsand their equivalents are intended to cover any such forms ormodifications as would fall within the scope and spirit of thedisclosure.

What is claimed is:
 1. A filter with a multi-layer substrate with heatdissipation, the filter comprising an acoustic wave device thatincludes: a support substrate; a piezoelectric layer; an interdigitaltransducer electrode on the piezoelectric layer; and a thermallyconductive layer configured to dissipate heat associated with theacoustic wave device, the thermally conductive layer having a higherthermal conductivity than the support substrate, the thermallyconductive layer being disposed between the support substrate and thepiezoelectric layer, and the thermally conductive layer having athickness that is greater than 10 nanometers and less than a thicknessof the piezoelectric layer; the filter being arranged as a band passfilter configured to filter a radio frequency signal.
 2. The filter ofclaim 1 wherein the support substrate is a quartz substrate.
 3. Thefilter of claim 1 wherein the acoustic wave device is configured togenerate an acoustic wave having a wavelength of λ, and the thickness ofthe thermally conductive layer is less than 0.03 λ.
 4. The filter ofclaim 1 wherein the piezoelectric layer has a higher thermalconductivity than the support substrate.
 5. The filter of claim 1wherein the support substrate includes at least one of silicon, aluminumnitride, silicon nitride, magnesium oxide spinel, magnesium oxidecrystal, or diamond.
 6. The filter of claim 1 wherein the acoustic wavedevice further includes a temperature compensating layer having apositive temperature coefficient of frequency, the temperaturecompensating layer being disposed between the piezoelectric layer andthe support substrate.
 7. The filter of claim 6 wherein the temperaturecompensating layer is a silicon dioxide layer.
 8. The filter of claim 6wherein the temperature compensating layer is disposed between thepiezoelectric layer and the thermally conductive layer.
 9. The filter ofclaim 6 wherein the temperature compensating layer is disposed betweenthe thermally conductive layer and the support substrate.
 10. The filterof claim 1 wherein the acoustic wave device further includes a firsttemperature compensating layer disposed between the piezoelectric layerand the thermally conductive layer, and a second temperaturecompensating layer disposed between the thermally conductive layer andthe support substrate.
 11. The filter of claim 1 wherein the thermallyconductive layer includes a metal.
 12. The filter of claim 1 wherein thethermally conductive layer has a thermal conductivity in a range from140 W/mK to 425 W/mK.
 13. The filter of claim 1 wherein the thermallyconductive layer has a thermal conductivity that is at least 10 times athermal conductivity of the piezoelectric layer.
 14. The filter of claim1 wherein the piezoelectric layer is a lithium tantalate layer.
 15. Thefilter of claim 1 wherein the filter is arranged such that a maximumsurface temperature of a filter chip that includes the filter is lessthan 60° Celsius during operation of the filter.
 16. The filter of claim1 wherein the acoustic wave device is a surface acoustic wave device.17. A surface acoustic wave device with a temperature compensatedmulti-layer substrate with heat dissipation, the surface acoustic wavedevice comprising: a support substrate; a piezoelectric layer; aninterdigital transducer electrode on the piezoelectric layer; athermally conductive layer configured to dissipate heat associated withthe surface acoustic wave device, the thermally conductive layer havinga higher thermal conductive than the support substrate, the thermallyconductive layer being disposed between the support substrate and thepiezoelectric layer, and the thermally conductive layer having athickness that is greater than 10 nanometers and less than a thicknessof the piezoelectric layer; and a temperature compensating layer havinga positive temperature coefficient of frequency, the temperaturecompensating layer and the interdigital transducer electrode beingdisposed on opposite sides of the piezoelectric layer.
 18. The surfaceacoustic wave device of claim 17 wherein the piezoelectric layer is alithium tantalate layer and the support substrate is a quartz layer. 19.The surface acoustic wave device of claim 17 wherein the surfaceacoustic wave device is configured to generate a surface acoustic wavehaving a wavelength of λ, and the thickness of the thermally conductivelayer is less than 0.03 λ.
 20. A radio frequency module comprising: aradio frequency switch configured to pass a radio frequency signal; asurface acoustic wave filter configured to filter the radio frequencysignal, the surface acoustic wave filter including a surface acousticwave resonator configured to generate a surface acoustic wave having awavelength of λ, the surface acoustic wave resonator including supportsubstrate, a piezoelectric layer, and a thermally conductive layerconfigured to dissipate heat associated with the surface acoustic waveresonator, the thermally conductive layer being disposed between thequartz substrate and the piezoelectric layer, and the thermallyconductive layer having a thickness in a range between 10 nanometers and0.03 λ; and a package enclosing the surface acoustic wave filter and theradio frequency switch.